Multi-row QFN packages (such as aQFN™) are enhanced versions of conventional QFN packages which allow the I/O number to approach that of a BGA-type chip-scale package (CSP). Multi-row QFN is often the preferred solution for electrical components of portable telecommunication devices such as IrDA, Bluetooth™, RFID, etc. for its superior thermal, electrical performance and reliability and miniaturized package size.
FIG. 1A is a schematic diagram showing a cross-sectional view of a multi-row QFN package 100 with multiple rows of pads. A die 102 is attached to the leadframe. Wires 106 electrically couple the die 102 to a plurality of wirebond posts 104 arranged at different distances to the die. Resin 108 bonds the die 102, the wires 104, the leadframe and isolated wirebond posts 104 together and protects them from damage. FIG. 1B is a schematic diagram showing both a top plan view and a bottom view of a multi-row QFN package with multiple rows of pads.
Compared to the multi-row QFN package, a QFN package with a single row of pads has the advantage that its simple arrangement makes it easier (and hence lower cost) to surface mount, reduces the possibility of solder bridging between I/Os and allows easier visual inspection of all the solder joints once soldered to a Printed Circuit Board (PCB). However, if only a single row of pads is used this can lead to very long wirebonds in the case of large numbers of I/Os and/or a small die (e.g. where there are more pads than can fit around the periphery of the die, the package is made larger so that the pads fit around the periphery of the package and wirebonds connect the die to these pads).
The embodiments described below are not limited to implementations which solve any or all of the disadvantages of known methods of forming a QFN package.